Modelling the Stress Relaxation Kinetics of Intercritically Deformed Austenite and Ferrite in C‐Mn Steel

In this study the softening kinetics of intercritically deformed C‐Mn steel have been characterised using the stress relaxation technique. In addition, the progress of softening has been monitored via optical microscopy of quenched samples. Physically based models for the softening kinetics of the separate phases were combined using the simple rule of mixtures, to predict the stress relaxation kinetics following intercritical deformation. Moreover, the strain and stress distribution developed during deformation has been taken into account using an analytical approach from the literature. Comparison of the model with experiments showed significant deviations. These were thought to be due to two effects concerning the role of phase interactions. Firstly, there was a region in the austenite phase having a low strain, leading to a fraction of non‐recrystallizing austenite. Secondly, the number of recrystallization nucleation sites was reduced. These two effects were tested by modifying the original model. The best agreement with experimental data was obtained when assuming the presence of a significant fraction of austenite that did not recrystallize.